HISTORY and ADVANTAGES
DRY CLEANING CARTRIDGE TYPE AIR FILTERS
The idea of cleaning air filters for reuse has been around for many years. Filters used in trucks, buses and construction equipment have been cleaned by some owners using either water (wet washing), or compressed air (blowing out); but both of these practices have potential pitfalls.
Wet washing an air filter with cellulose (paper) media results in a change in the media; and could lead to a failure of the filter, allowing dirt to be bypassed. Wet washing also leaves a residue behind in the pleats of the filter that increases the pressure drop across the filter and shortens the usage cycle time.
Blowing out an air filter with a typical compressed air line can result in actually blowing a hole in the filter media. This occurs because the compressed air pressure is not regulated, and all of the air is concentrated on a small point of the media. Any holes in the media, of course, would allow dirt to be bypassed.
It has only been since the 1990s that acceptable ways of dry cleaning cartridge air filters have been developed. The dry cleaning process does use compressed air; but the air pressure is regulated, and specially designed nozzles diffuse the impact on the media. The effect of the compressed air is also enhanced by agitation of the filter; and a complimentary vacuum system that passes additional air through the filter media, and removes the dirt for collection in a separate container.
An interesting phenomenon associated with air filters is the fact that they have to be used for a period of time, and get a little dirty, before they reach their maximum efficiency level. This break-in period allows a porous pre-coat, or cake, to build up on the filter; and this in turn is what is needed for the filter to reach its maximum filtering efficiency.
In dry cleaning a filter with a properly designed system, if any given particle of dirt is loosened from the media, it will be removed from the filter. This means that any dirt left in the filter after dry cleaning (normally less than 1%), is left in place where it remains part of the original pre-coat. Then when the dry cleaned filter is put back into use, it has already been partially broken-in; and its efficiency is actually better than a brand new replacement filter. This increased efficiency has been confirmed with tests conducted by independent laboratories.
Over the last six years, the Zaiser 2000 Series of cartridge air filter cleaning machines have been proven to be the best technology available for dry cleaning air filters, and this type of cleaning is recommended and supported by some filter manufacturers. The Zaiser 2003 Model is the only machine available that is specifically designed to clean filter cartridges from industrial dust collectors, and powder paint recovery systems. The Zaiser machines are covered by two United States patents; numbers 5,584,900 and 5,915,439.